Engines and avionics, but the rocket bodies, fairings, etc., are made in NZ and final assembly is there. In this interview: https://www.youtube.com/watch?v=Nj9BncsgvuQ the CEO talks about how that has been advantageous because apparently there's a large talent pool in carbon composite fabrication in NZ, and that while there are eventually plans to also launch from the US, when they do they'll still be making bodies in NZ and shipping them, and doing final assembly with US-made engines on the US side for those launches.
Yep, the America's Cup success lead to recognition of NZ's somewhat burgeoning super-yacht industry, which in turn fed back more talented craftsman, fabricators, designers.
Speaking of carbon composite fabrication talent in NZ, I remember at an airshow in NZ a few years ago there was a company making a helicopter with an entirely composite airframe. Not sure what ended up happening to it, but it was interesting to see such cutting edge technology coming coming out of such a small company with minimal funding.
John Britten's superbike in the 1990s was also a pioneer for all sorts of composite manufacturing
Us Kiwis have always been good at that kind of thing though. There's actually a very healthy aviation technology and manufacturing industry here, especially for such a small country.
Was just listening to an interview with Peter Beck. He clarifies the US-NZ question. Short answer is it is both, I had my proportions off with being more (3/4) American now. It's been American company since 2012. The US factory is 3 times larger than the NZ factory and makes stuff we're can't do here.